312 CHEMICAL DISCOVERY AND INVENTION 



Further there are reasons for believing that a number of 

 carbon atoms joined together do not really range themselves in 

 straight rows as it is convenient to write them on paper, for 

 instance, 



Cxi 3. C xl 2- Cxi 2- C xl 2- Cxi 2 . Cxi 3, 



but that in such a case the chain occupies in space the form of a 

 spiral. Hence there is a tendency to the formation of closed 

 chains or rings as in the case of benzene, C 6 H 6 , which is repre- 

 sented by the formula below : 



CH CH 



HC 



CH 



CH 



or 



HC 



CH 



CH 



CH 



In this case the expression is required so frequently in writing 

 the formula for organic compounds that it is customary to 

 reduce it to the skeleton without symbols thus : 



which is generally understood without writing the symbols for 

 the several atoms. 



The first synthetic dye was produced accidentally by W. H. 

 Perkin in 1856 when engaged in a research having a different 

 object in view. The product was called mauve from the colour 

 which resembles that of the flower of the mallow (French = 

 mauve), and although it has long ceased to be manufactured as 

 a dye for silk and wool, owing to its tendency to fade in sun- 

 light, it has been used in more recent times for colouring postage 

 stamps. 



